Method of preparing high melting point asphalt and high quality bright stock from mixed base residuum



Patented 15, m40

` UNITED `STATES" PATENT OFFICE Y 2,217,727 METHOD oF rnEPAnnvG manMELTING POINT ASPHALT SIDUUM AND BRIGHT STOCK FROM HIGH QUALITY MIXEDBASE RE- Arthur B. Brown and Frank C. Croxton, Hammond, Ind., andBernard Ginsberg, Chicago, I11.. assignors to Standard Oil Company,Chicago, Ill., a corporation oi Indiana .Y Application June a 193s,serian No. 212,656

with the acid treating and neutralization steps.v

A further object is to provide an improved method and means for nishingan acid-treated filter stock to obtain petrolatums and bright stocks ofimprovedV cast, color stability andoxidation stability. Other objectswill be apparent yas the detailed description of the invention proceeds.

In the operation 0f the deasphalting plant at Whiting, Indiana, it wasdiscovered that the amount of propane admixed with 'the oil during theacid treating step had a profound effect on the neutralizing and nishingsteps. When operating with a propane-to-oll ratio below 3:1 it was foundthat ythe sour oil could not be effectively neutralized, even whenexcess caustic and inti-I mate mixing was employed. This phenomena isunexplainable in'the light of our present knowledge and experience, butit is evident that the propane has some effect in the acid treating stepother than that of a simple diluent or thinner.

The neutralization difliculty is not, as might be expected, afunction-of the amount of acid used,-it ls a function of the propaneratio during the acid-treating step. However, the amount of acid used isimportant from the standpoint of color stability. If'large amounts ofacid .are employed the oil requires little or no clay -to meet colorspecifications, but such excessively treated oils are not stable againstoxidation, and they. tend to go oli color on standing, We have foundthatnot only the propane ratio, but also the amount of acid used must beregulated within close limits, and that the nishing with clay must alsobev within certain limits if a stable,

high quality bright stock is to be produced.

In practicing our invention we regulatel the propane ratio in thedeasphalting step to produce asphalt of the desired melting point,penetra.

tions etc. Such ratios may, for instance, be in the range of 2:1 toabout 4:1. Subsequent to the deasphaltingy step'and prior to theacid-treating i step .we add suillcient propane (if'addition isnecessary) to bring the propane-tofoil ratio up to at least 3:1, andpreferably to 3.5:1 or more.

The amount of acid should be sufcient to decolorize the oil onlypartially, and we have found that .25 to .3 pound of 93% sulfuricacidior its equivalent) per gallon of original charging stock meets thisrequirement when deasphalting is effected in about 3 to 4 volumes ofpropane at about `90 tti-115 F., preferably at about'llOV F. When lesseramountsof propane are employed in the deasphalting step. the amount ofacid required maybe increased to about .3 to .7 pound per gallon of oil.The amount of acid should be regulated so that in the claying step afilter yield of about 400 to 1000, preferably about 600 to 700 gallonsper ton is obtained when using average clayA (this may be increased to1500 gallons Withnew No. l clay). This Aamount of claylng is essentialfor color and oxidation stability. We prefer to strain the oil through aspent lter `prior to the dewaxing or cold settling step, and

finally to percolate the wax-free oil or petrolatum in a fresh lter atabout 100 to 180 F.

` Another feature of our invention, particularlyl when it is applied totherefining of petrolatum,

is our method of handling and eliminating sludge pepper. When heavy oilsor petrolatums are acid-treated ln propane we have found that thetreated product tends to suspend a sludge pepper" which has-to beremoved before proper neutralization can be eiected. We have Ydiscovered that this sludge pepper may be removed by further settling.if sufficient propane diluent is employed and suiliclent settling timeis allowed. Our method includes the provision of a sludge pepper"settling step with a propaneto-oil ratio of at least 3.5:1 and in asettling zone of the type used for deasphalting orcaustic settling.

y The invention will be more clearly understood from the followingdetailed description read in connection with the accompanying drawingwhich forms a part of `this specification and which illustrates a owdiagram of our improved system l for bright stock manufacture.

In our preferred embodiment we will describe the preparation of brightstock from a Mid-Continent residuum reduced to about 20% bottoms andhaving a viscosity of about 350 to 400 seconds Saybolt at 210 F. Itshould be understood, however, thatth'el inventlon'isequally applicableto other charging stocks and to oils of widely varying compositionm l.

A Mid-Continent reduced crude having a viscoslty @f about 365 to 37oseconds saybolt artt 210 F. is charged to the system through line I0 bymeans of pump Il and is admixed with about 21/2 volumes of propane from!storage `tank I2, pump I3 and line I4. This mixture is heated inexchanger or heater I5 to a temperature of about 90 to 115 F.,preferably about 100 F. to 110 F. and then introduced into asphaltsettler I6 which is maintained at about 200 to 350 poundspressure,-suiiicient to prevent substantial vaporization of propane.With this low propane ratio a high melting asphalt of low penetration isseparated out and withdrawn from the base' of the settler through lineI1 to a conventional asphalt depropanizer system.

The propane soluble fraction from the asphalt settler is withdrawnthrough line I8 to rst acid sludge settler I9 but before it isintroduced intothe settler it is admixed with enough propane from lineto bring the propane-to-oil ratio up to at least 3: 1, and preferably toabout 3.5: 1. Instead of using fresh acid at this point We introducecycle sludge through line 2I from the second acid sludge settler. Theintimate mixture of deasphalted oil, propane and cycle sludge'passesdown through thefunnel-like center portion 22 'of the rst acid sludgesettler into the quiescent zone in the lower part of the settler. Sludgeis withdrawn from the base of the settler through line 23 to aconventional sludge depropanizer and hydrolyzer. Sour oil from theupper-part of the quiescent zone is withdrawn through line 24 to theupper part of second acid sludge settler 25. The fresh acid isintroduced through line 26 preferably in amounts of about .2.to .5 poundof 93% acid (or equivalent amounts of 98% acid,etc.) per gallon oforiginal oil charged. The amount of acid in all cases should be soregulated that the oil can be finished to the desired color with apercolation yield of about 400 to 1000 gallons per ton of average clay.It may also be desirable to add -additional propane to line 24 throughline 21,

particularly if the propane ratio was low in the rst acid sludgesettler. It is most important that the propane-to-oil ratio in thesecond settler be at least 3 or 31/2:1.

`The'sludge from the second settler is recycled through line 2l to lineI8, as hereinabove described. If the sour oil from the upper part of thequiescent zonev in the second settler is substantially free of sludgepepper, it is withdrawn through line 28, admixed with caustic from line29, and .introduced into caustic settler 30. The

amount of caustic will vary with different stocks and amounts of acidused, but we usually employ about .035 pound per gallon (based onoriginal oil charged) in the form of a 3% solution of sodium hydroxide.The used caustic solution is withdrawn from the base of the settler.through line 3l, and the neutralized oiiis withdrawn.

through lines 32 and 33 to propane still 34. Propane is removed from thevtop of the still through line 35 and recovered for reuse. Depropanizedoil is withdrawn through line 36 todepropanized filter stock storagetank 31. n

Filter stock from tank 31 is withdrawn -by pump 38 and admixed withlight naphtha with" drawn from tank 38 by pump 48, the blend of naphthaand filter stock being introduced through lines 4I and 42 to the top ofa used clay nlter 43. The purpose of passing the solution .through theused filter is' to strain out certain color bodies and impurities,thereby improving the quality of the petrolatum to be later .separated.The filter stock solution fromused filter 75 43'is withdrawn lines 44and 45V to cold settling tank 46 wherein the solution is graduallychilled to low temperatures for the settling of through line 50, heater5I and line 52 to fresh clay lter 53 where it is percolated through clayat about 100 to 180 F., preferably at about 110 F. to give a yield ofabout 400 to 1000 gallons per ton, preferably about 500 to 700 gallonsper ton. From this clay filter the oil is passed through lines 54, 55and 56 to naphtha-reducing still 51, the naphtha being returned throughline 58 and condenser 59 to naphtha storage tank 39, and the iinishedbright stock being withdrawn through line 60 to storage tank 6 I Aftersettler 46 has been charged, as hereinabove described, the clay infilter 43 is revivied and/or fresh clay is added to this lter. Clayfilter 53 now becomes the spent filter and the naphtha iilter stocksolution from line 4I is charged through lines 4I and 62 into spentfilter 53 for the straining step. 'I'he strained oil is withdrawnthrough lines 54 and 53, 44 and 64 to cold settling tank 65. After thesolution has been chilled and settled in this tank the clear solution iswithdrawn todewaxed solution tank 48 through line 66 .and the petrolatumis withdrawn from the.

base of the settler through line 61. 'Ihe dewaxed solution now passes`through line 50, heater 5I and line 68 to fresh filter 43, the clayedsolution being withdrawn through lines 69 and 56 to the naphtha-reducingstill hereinabove described.

The strainingfcold settling and filtering operations hereinabovedescribed are designed for use in low pressure equipment. When highpressure equipment is available the use of naphtha may be entirelyavoided and the neutralized cil from caustic settler 30 may be passeddirectly through lines 32, 18, 4I and 42 for straining in filter 43, orlines 32, 10, 4I and 62 for straining iu clay filter 53. Somewhat higherfilter yields may be obtained by the straining and subsequent filtrationY in propane solution, but here again the temperature should bemaintained at about 100 to 110 F.

for maimum eiliciency.

'tion arid is characterized by a low carbon residue and an acidity whichis so low that it 'is negligible.

By regulating the propane ratio in the acid treating step subsequent tothe deasphalting step, we have made it possible to use low propaneratios in the deasphalting step without interfering with the acidtreating and neutralization steps. This enables the production of highquality asphalts in addition to the high quality bright stocks.

By operating at about 100-115 F. on a 20% M. C. residuum with a propaneratio lower than 3:1 we can produce an asphalt with a melting pointabove' 170" F. and a penetration at '17 F. of less than 5. By blendingthis hard asphalt in the acid treating step, neutralization can beeasily eil'ected.

When petrolatums .or heavy oils are acidtreated it sometimes happensthatthe sour oil from the second settler contains appreciable Vamounts `ofsludge pepper vwhich is suspended or emulsified in the sour oil andwhich, unless it is removed, seriously impairs the quality o f thenished oil or petrolatum. We have discovered that this pepper" can bestbe removed by increasing the propane ratio to atleast 3.5:1 and settlingthe .pepper in a drum of the type used for settling asphalt andused'caustic. If the asphalt settler is available this vessel may beused for the pepper settle and further equipment (except for thenecessary lines, valves,

i sour'oil or petrolatum thru line 1| to pepper settler 12, additionalpropanebeing introduced thru line I3 if necessary. The sludge pepper issettled'and withdrawn thru line Il and may be depropanized andhydrolyzed with the material. fromline 23. The pepper-free oil orpetrolatum is returned by line to the caustic mixer and thence toycaustic settler 30; as hereinabove dewscribed.

Thus, the propane-to-oil ratio should be a least 3:1 in the acidtreating step. but if in this f stepa. sludge pepper n L'suspemiea inthe on, additional propane may be added and this pepper gsettled outbefore the neutralization and further nishing steps. While we havedescribed in deaarmav Y pumps, etc.) will not be necessary. .We may,however, close the valve in line 28 andpass the tail a preferredembodiment of our invention, it

should be understood that we do not limit ourpane-v-to-residuum ratio ofless than 3:1 at a -temperature of about 90 to 115 E., addingenoughpropane tothe deasphalted oil vtogincrease the propane-to-oil ratio toat least 3:11, treating the oil in this propane s'olutionwitlr acid at atemperature of about 90 to 110 F. with an amount of acid of about .2 to.7 pound of 93%-98% sulfuric acid per gallon of oil, neutralizing thesour oil and filtering the neutralized oil through lclay at about 100 to180 F. to .obtain clay yields of about 400 to 1000 gallons per ton ofordinary clay.

2. The `method of claim 1 which includes the further step of dewaxing.the neutralized oil prior tothe final ltering through clay.

3. The method of claim 1 which includespthe' steps' of depropanizing theneutralized oil, `mixing the depropanized oil withnaphtha, strainingthe-naphtha solution through a spent iilter, dewaxing the strained:naphtha solution, and subjecting the dewaxedso'lution to :thefiltration step at about 100 to 180 F. vto obtain clay yields of about400 to 1000 gallons per tonA of vaverage clay.

4. The method of -obtaining high melting point low penetration asphaltsand high quality bright stocks which comprises deasphalting a mixed baseresiduum with a propane-to-residuuinratio less than 3:-1, addingadditional propane to the deto about 3:1 to 3.5:1, 'acid-treating theoil in the resulting propane solution with about .25 to .7

pound'of 90% to 100% sulfuric acid per gallon of oil treated,neutralizing the acid-treated oil and treating said oilv with clay.

ARTHUR BROWN. FRANKg-C. CROXTON. BERNARD GINSBERG.

